1. Field of the Invention
The present invention relates to a light emitting diode (LED) backlight apparatus for supplying a white light source by mixing monochromatic LEDs to a display device. More particularly, the invention relates to an LED backlight apparatus which includes a first LED row and a second LED row alternating on a substrate. The first LED row includes red LEDs disposed adjacent to opposed peripheries of a substrate, with green, blue and red LEDs alternately disposed between the red LEDs adjacent to the peripheries. The second LED row includes a similar arrangement of LEDs with blue LEDs disposed adjacent to the opposed peripheries of the substrate. The backlight apparatus regulates the amount of radiation directly incident upward from a position of the red and blue LEDs adjacent to the opposed peripheries to be smaller than the amount of radiation from the rest of the LEDs, thereby eliminating color deflection occurring at the opposed peripheries of a light guide plate.
2. Description of the Related Art
In general, a Liquid Crystal Display (LCD) does not have a light source of its own, thus requiring an external illumination which typically is a backlight apparatus. The backlight apparatus illuminates the LCD from the back using Cold Cathode Fluorescent Lamp (CCFL) and LED as a light source.
An LED backlight apparatus using LED as a light source can be classified into an edge type and a direct illumination type. In the edge type, a light guide panel made of transparent material is disposed on a substrate, and light from LEDs disposed at one side or both sides of the light guide panel is incident into the light guide panel to be propagated upward by an optical pattern formed on a bottom of the light guide panel, thereby backlighting the LCD. On the other hand, in the direct illumination type, a plurality of LEDs are installed underneath the LCD to backlight the LCD. These two types have merits and demerits, respectively, but the direct illumination type is especially advantageous for backlighting a large area with high output.
FIG. 1 is a schematic exploded perspective view illustrating a conventional LED backlight apparatus, and FIG. 2 is a sectional view illustrating the LED backlight apparatus shown in FIG. 1.
The conventional LED backlight apparatus 10 includes a substrate 12, a plurality of LEDs 14R, 14G and 14B disposed on the substrate, a side reflector 20 disposed in opposed peripheries of the substrate 14 and a planar optical element 30 disposed above the substrate 14. An LCD 40 is disposed above the planar optical element 30, and the light beams generated from the LEDs 14R, 14G and 14B are mixed to form white light, which passes through the planar optical element 30 to provide backlight for the LCD 40. In this specification, the planar optical element 30 designates any optical element including a diffusion plate (e.g. a microprism sheet) and an optical filter which processes the light beams emitted from the LEDs 14R, 14G and 14B before they are incident onto the LCD 40 disposed above.
The conventional LED backlight apparatus 10 has following disadvantages. As shown in FIG. 3, color deflection occurs at the opposed peripheries of the LCD 40. That is, the opposed peripheries of the LCD 40 exhibit a specific color, which is due to the fact that the light beams from the red LEDs 14R or the blue LEDs 14B disposed at the peripheries are predominant over and do not mix well with other colors of light beams.
Therefore, in order to overcome such a problem, the planar optical element 30 should be disposed apart in a sufficient interval from the underlying LED 14. Alternatively, the planar optical element 30 should be formed sufficiently thick or in more layers.
However, increasing the interval between the planar optical element 30 and the LEDs 14 increases the thickness of the LED backlight apparatus 10. In addition, forming the planar optical element 30 sufficiently thick or in more layers results in increase in the weight or costs of the LED backlight apparatus 10.